Variable and poor-quality drug labeling has been cited as a leading cause of medication errors and adverse drug events. This is an especially important issue in pediatrics, as more than half of US children are exposed to one or more outpatient medications in a given week, and studies suggest that over half of caregivers make errors when dosing liquid medications for children. Administering pediatric medications is frequently a difficult task for parents, in large part due to reliance on liquid formulations requiing the use of confusing, and often complex, measurement devices. Use of different units of measurement (milliliter, teaspoon, and/or tablespoon units) with variations in associated abbreviations, and the variability of measuring devices (type, markings, capacity), are sources of parent confusion. Low health literacy is linked to caregiver misunderstanding. Despite high error and utilization rates for outpatient pediatric medications, research examining strategies to prevent medication errors have focused largely on adults and on inpatient populations. The ability to understand pediatric medication instructions is a critical health literacy and patient safety concern. Recently, the US Food and Drug Administration recognized the importance of this issue and released new guidelines to promote improved labeling and measuring devices for pediatric liquid medications. While these recommendations are an essential first step, evidence is needed to support the development of 'best practices' for designing optimal instructions and devices, especially for parents with limited literacy and/or limited English proficiency. Our stud objective is to identify evidence-based 'best practices' for labeling and dosing prescription and over-the-counter pediatric liquid medications in order to promote safe, appropriate use. A series of experiments will first be conducted to examine the efficacy of specific dosing and measurement strategies for improving parent understanding and use of pediatric liquid medications, including examining the impact of milliliter-only label instructions and devices, as well as the potential role for pictographic dosing diagrams. Findings will be merged with existing evidence-based health literacy 'best practices' for medication labeling to develop a comprehensive, patient-centered strategy for the labeling and dosing of pediatric liquid medications. The effectiveness of the patient-centered strategy will then be evaluated as part of a randomized controlled trial among English and Spanish-speaking parents whose children have been newly prescribed oral liquid antibiotics in a pediatric emergency department setting. Secondary aims of the study include extending the body of literature on health literacy and pediatric medication use, and generating a policy road map for achieving and implementing labeling and dosing standards for pediatric liquid medications.